Spherical and nearly spherical view imaging assembly

ABSTRACT

The present invention describes several embodiments of electro-optical assemblies, which are capable of capturing full or nearly full spherical field of view. The present invention presents improvements of the prior art methods by unifying several methods to achieve coverage of a large field of view. The present invention provides a method for utilizing the concept of reflective surfaces and combining two image capture devices to achieve an even larger field of view than those presented previously.

This application claims the benefit of U.S. Provisional Application No:60/379,768 filed 14 May 2002 and incorporates the same by reference.

FIELD OF THE INVENTION

The present invention relates to the field of wide angle imaging. Morespecifically, it relates to electro-optical structures that enablecapture of a hemispherical, nearly spherical or spherical scene.

BACKGROUND OF THE INVENTION

Imaging of a large field of view at the same instant is required for awide variety of applications. Security cameras, for instance, areusually very limited in their field of view; therefore rotation/pan-tiltmechanisms are often implemented to enable accumulative coverage of thedesired wide field of view. Inner body imaging during medical endoscopyprocedures also represents a need to view as large field of view aspossible, in order to achieve proper orientation while maneuvering themedical endoscope inside the body. Additional applications exist, andthey all suffer from the currently limited field of view, which isprovided by the lenses that are implemented in the image capture device.

As a result of the specified problems, prior art has provided methods ofenlarging the field of view which is covered by an image capture device,by utilizing axi-symmetric reflective surfaces, which reflect acylindrical field of view towards the image capture device. An examplefor such a method is described in Publication No. US 2002/0126395.

A more complex method is described in Publication No. US2001/0010555 andincludes a design of a mirror assembly, comprised of two reflectivesurfaces and provides coverage of a cylindrical field of view.

Additional methods were presented, in order to enlarge the field of viewbeyond cylindrical. U.S. Pat. No. 6,028,719 describes the use of anaxi-symmetric reflective surface with a hole in its center to achievecoverage of two scenes—a cylindrical scene which is reflected from thesurface, and an additional scene, which is above the cylindrical scene,which penetrates through the hole and captured simultaneously by thesame image capture device, thus a hemispherical field of view may becaptured.

An improved method for capturing a hemispherical field of view isdescribed in publication no. WO 02/059676, which is incorporated hereinby reference.

Furthermore, the art has presented a method for acquiring a cylindricalfield of view, together with an optically zoomed sector simultaneously.The method described in Publication No. WO 03/026272, which isincorporated herein by reference, makes use of an axi-symmetricreflective surface that reflects a cylindrical field of view towards animage capture device and an additional reflective surface which reflectsan optically zoomed sector towards the same image capture devicesimultaneously.

Additional methods which rely on the use of an axi-symmetric reflectivesurface were presented, all rely on the concept of reflecting a largefield of view towards an image capture device, and some includeperforming image processing to convert the image to a shape suitable fora human viewer.

It is therefore an object of the present invention to providesignificant improvement to wide-angle image capture devices, byenlarging the field of view which is covered simultaneously.

It is further an object of the present invention to provideelectro-optical structures that provide hemispherical, nearly sphericalor spherical field of view coverage.

It is yet another object of the present invention to provide a methodfor achieving optical zoom of a sector, while continuously imaging anearly spherical field of view.

Other objects of the invention will become apparent as the descriptionproceeds.

SUMMARY OF THE INVENTION

The present invention presents a nearly spherical imaging assembly. Inits basic embodiment the spherical imaging assembly of the inventioncomprises:

-   -   a. An axi-symmetric lens, which provides at least a reflection        of a cylindrical field of view;    -   b. A first image capture device, which is positioned coaxially        with said axi-symmetric lens; and    -   c. A second image capture device, which is set to capture an        image that is at least partially different from the image        captured by said first image capture device.

In this embodiment, light rays from a first, cylindrical, scene arereflected by the axi-symmetric lens and captured by the first imagecapture device and light rays from a second scene, at least partiallydifferent from the first scene are captured by the second image capturedevice.

The first image capture device is directed towards the axi-symmetriclens and is set to capture the image that is reflected by theaxi-symmetric lens. The second image capture device is positioned eitheropposite to the first image capture device or opposite to theaxi-symmetric lens. In either case, the light rays from the firstcylindrical scene are reflected by the axi-symmetric lens towards thefirst image capture device. The second image capture device can bepositioned coaxially with the first image capture device.

In another embodiment of the invention, the nearly spherical imagingassembly further comprises a reflective surface positioned coaxiallywith the axi-symmetric lens and directed towards the axi-symmetric lens.In this embodiment the axi-symmetric lens comprises a transparent areain its center and the first image capture device is directed towards thereflective surface and set to capture the image that is reflected by thereflective surface after penetrating the transparent area in theaxi-symmetric lens. The second image capture device is positionedopposite to the reflective surface. In this case, light rays from afirst, cylindrical, scene are reflected by the axi-symmetric lenstowards the reflective surface, are then reflected from the reflectivesurface, and travel through the transparent area towards the first imagecapture device. The second image capture device can be positionedcoaxially with the first image capture device.

In another embodiment the nearly spherical imaging assembly of theinvention further comprises:

-   -   a) a transparent area in the center of the first axi-symmetric        lens;    -   b) a reflective surface, comprising a transparent area in its        center, positioned coaxially with the first axi-symmetric lens,        directed towards the first axi-symmetric lens.    -   c) A second axi-symmetric lens providing at least a reflection        of a cylindrical field of view, positioned opposite to the first        axi-symmetric lens.

In this embodiment the first image capture device is directed towardsthe reflective surface and set to capture the image that arrives fromthe direction of the reflective surface after penetrating thetransparent area in the first axi-symmetric lens. The second imagecapture device is, positioned coaxially with the second axi-symmetriclens, directed towards the second axi-symmetric lens, and set to capturethe image that is reflected by the second axi-symmetric lens. With thisoptical arrangement, light rays from a first, cylindrical, scene arereflected by the first axi-symmetric lens towards the reflectivesurface, reflected from the reflective surface towards the transparentarea in the first axi-symmetric lens, towards the first image capturedevice, and are captured by the first image capture device. Light raysfrom a second scene penetrate the transparent area in the reflectivesurface, travel toward the transparent area in the first axi-symmetriclens, penetrate the transparent area, and are captured by the firstimage capture device. Additionally, light rays from a third scene, atleast partially different from the first scene, are reflected by thesecond axi-symmetric lens towards the second image capture device andcaptured by the second image capture device. The second axi-symmetriclens is positioned coaxially with the first axi-symmetric lens.

A variation of the previous embodiment of the nearly spherical imagingassembly of the invention further comprises optical lenses located atthe exterior of the reflective surface, coaxially with the transparentarea in the reflective surface. These optical lenses are designed tocontrol the aperture of the second scene that is captured by the firstimage capture device.

Another embodiment of the nearly spherical imaging assembly of theinvention further comprises a reflective surface located around thecentral axi of symmetry of the axi-symmetrical lens. This arrangementprovides an optically zoomed reflection of a limited sector towards thefirst image capture device. In this embodiment, the first image capturedevice is directed towards the axi-symmetric lens and set to capture theimage that is reflected by the axi-symmetric lens. The second imagecapture device is positioned opposite to the axi-symmetric lens. Withthis optical arrangement, light rays from a third scene comprising apartial sector of the first scene are optically zoomed and reflected bythe reflective surface towards the first image capture device and arecaptured by the first image capture device. The second image capturedevice can be positioned coaxially with the axi-symmetric lens.

Another embodiment of the spherical imaging assembly of the inventionfurther comprises:

-   -   a) a transparent area in the center of the first axi symmetric        lens;    -   b) a first reflective surface, comprising a transparent area in        its center, located coaxially with the first axi symmetric lens        and directed towards this lens;    -   c) a second axi symmetric lens, comprising a transparent area in        its center, providing at least a reflection of a cylindrical        field of view. This second axi symmetric lens is positioned        opposite to and coaxially with the first axi symmetric lens;    -   d) A second reflective surface, comprising a transparent area in        its center, located coaxially with said second axi symmetric        lens and directed towards this lens.

In this embodiment the first image capture device is directed towardsthe first reflective surface and set to capture the image that arrivesfrom the direction of the first reflective surface after penetrating thetransparent area in the first axi-symmetric lens. The second imagecapture device is positioned coaxially with the second axi-symmetriclens, directed towards the second reflective surface, and set to capturethe image that arrives from the direction of the second reflectivesurface after penetrating the transparent area in the secondaxi-symmetric lens. Thus, light rays from a first, cylindrical, sceneare reflected by the first axi symmetric lens towards the firstreflective surface, reflected towards the transparent area in the firstaxi-symmetric lens, penetrate the transparent area, and are captured bythe first image capture device. Simultaneously, light rays from a secondscene, which is at least partially different from the first scene,penetrate through the transparent area in the first reflective surface,travel towards the transparent area in the first axi-symmetric lens, andare captured by the first image capture device. Simultaneously lightrays from a third, cylindrical, scene are reflected by the second axisymmetric lens towards the second reflective surface, then reflectedtowards the transparent area in the second axi-symmetric lens, penetratethe transparent area, and are captured by the second image capturedevice. Also, simultaneously, light rays from a fourth scene, which isat least partially different from the third scene, penetrate through thetransparent area in the second surface, travel towards the transparentarea in the second axi-symmetric reflective lens, and are captured bythe second image capture device.

All the above and other characteristics and advantages of the inventionwill be further understood through the following illustrative andnon-limitative description of preferred embodiments thereof, withreference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically describes an imaging assembly that enables coverageof at least a hemispherical field of view;

FIG. 2 schematically describes an imaging assembly that enables coverageof a nearly spherical field of view;

FIG. 3 schematically describes another imaging assembly that enablescoverage of at least a hemispherical field of view;

FIG. 4 schematically describes yet another possible design of an imagingassembly that enables coverage of a nearly spherical field of view;

FIG. 5 schematically describes an imaging assembly that enables coverageof a nearly spherical field of view, together with an optically zoomedsector; and

FIG. 6 schematically describes an imaging assembly that enables coverageof a full spherical field of view.

DETAILED DESCRIPTION OF THE INVENTION

The present invention describes several embodiments of electro-opticalassemblies, which are capable of capturing full or nearly full sphericalfield of view.

It is stressed that the present invention presents improvements of theprior art methods by unifying several methods to achieve coverage of alarge field of view. The present invention provides a method forutilizing the concept of reflective surfaces and combining two imagecapture devices to achieve an even larger field of view than thosepresented previously. Issues such as mechanisms for positioning andfixating the lenses in relation to the image capture device are notdiscussed, as those have been presented in prior art and are familiar tothose skilled in the art.

FIG. 1 demonstrates a first embodiment of a nearly spherical field ofview imaging assembly. According to this design, an axi-symmetricreflective lens (1) is positioned to reflect a first scene of acylindrical field of view towards a first image capture device (2). Thefirst image capture device (2) is positioned coaxially with thereflective lens (1), directed towards the reflective lens and set tocapture the image reflected from the reflective lens (1). A schematicpath (3) describes a light ray, which arrives from a direction close tothe image capture device (2). The ray (3) hits the reflective lens (1)and is reflected towards the image capture device (2). A secondschematic path (4) describes a light ray which represents the limit ofthe field of view which is covered by the lens (1). It is stressed thatthe first ray (3) and the second ray (4) are schematic, their path isschematic and they are dependant on the exact shape, structure andcharacteristics of the lens (1). It is further stressed that the raysdescribed represents the limits of the field of view which is covered bythe lens (1) therefore, every ray which originates between rays (3) and(4) will also be reflected by the lens (1) and captured by the firstimage capture device (2), therefore a cylindrical field of view isreflected by the lens (1) and captured by the first image capture device(2).

A second image capture device (5) is positioned coaxially with the firstimage capture device (2), opposite to it and preferably in conjunctionwith it, so it is directed to the opposite side, and set to capture asecond scene. The second image capture device (5) may be equipped with awide angle lens, such as a fish-eye lens, in order to enable coverage ofa relatively large field of view.

The arrangement described in this figure provides a cylindrical field ofview which is captured by the first image capture device (2) and anadditional field of view which is captured by the second image capturedevice (5). The two fields of view together provide at least ahemispherical field of view.

FIG. 2 demonstrates a second embodiment of an imaging assembly whichenables coverage of a nearly spherical field of view. According to thepresent figure, an axi-symmetric reflective lens (6) is positioned toreflect a first scene of a cylindrical field of view towards a firstimage capture device (7). The first image capture device (7) ispositioned coaxially with the reflective lens (6), directed towards thereflective lens (6) and set to capture the image reflected from thereflective lens (6). A second image capture device (8) is preferablypositioned coaxially with the reflective lens (6), opposite to it, andpreferably in conjunction with it, so that it is directed to theopposite side, and set to capture a second scene. The second imagecapture device (8) may be equipped with a wide angle lens, such as afish-eye lens, in order to enable coverage of a large field of view.

The arrangement described in this figure provides a cylindrical field ofview which is captured by the first image capture device (7) and anadditional field of view which is captured by the second image capturedevice (8). The two fields of view together provide a nearly sphericalfield of view.

FIG. 3 is a third embodiment of an imaging assembly, which enablescoverage of a nearly spherical field of view. According to this figure,an axi-symmetric reflective lens (9) is positioned to reflect a firstscene of a cylindrical field of view towards a reflective surface (10).A transparent area is formed in the center of the reflective lens (9).The reflective surface (10) is placed opposite to the reflective lens(9), and coaxially with it, so that the view that is reflected from thereflective lens (9) is reflected again from the reflective surface (10)towards the transparent area that exists in the center of the reflectivelens (9). A first image capture device (11) is placed coaxially with thetransparent area, so that it is set to capture the view that is doublyreflected from the reflective surface (10) and passes through thetransparent area. A second image capture device (12) is positionedopposite to the reflective surface (10), preferably in conjunction withit, directed towards the opposite side and set to capture a secondscene. The second image capture device (12) may be equipped with a wideangle lens, such as a fish-eye lens, in order to enable coverage of alarge field of view.

The arrangement described in this figure provides a cylindrical field ofview which is captured by the first image capture device (9) and anadditional field of view which is captured by the second image capturedevice (12). The two fields of view together provide a nearly sphericalfield of view.

In the designs shown in FIGS. 1, 2, and 3, one of the image capturedevices is used to capture a cylindrical field of view, which isreflected by one or more reflective surfaces and captured on the focalplane array of the image capture device as an image of a circular shapehaving certain aberrations. Those aberrations can be corrected bydesignated computer software that can also create an image of a shapesuitable for viewing and understanding by the viewer. The other imagecapture device is used for direct capture of a second scene, which ispreferably continuous or overlapping with the first scene. The output ofthe two image capture devices may be presented separately, or may beprocessed to form a single unified image of the entire field of view.

FIG. 4 demonstrates a fourth possible design of an imaging assemblywhich enables coverage of an almost full spherical field of view imagingassembly. This design makes use of prior art design of a nearlyspherical field of view imaging device, described in publication WO02/059676. The present design utilizes the design described in thereference and incorporates additional electro-optical elements in orderto enlarge the field of view that is covered. In the present design afirst image capture device (13) is used to capture a first scene of anearly spherical field of view. The first image capture device (13) isincorporated as part of a nearly spherical field of view imaging systemdescribed in the said references. Coaxially with the first image capturedevice (13) and opposite to it, an axi-symmetric reflective lens (14) ispositioned. The said axi-symmetric reflective lens (14) is set toreflect a second scene of a cylindrical field of view towards a secondimage capture device (15), which is positioned coaxially with thereflective lens (14) and directed towards it. The second scene ispreferably continuous or overlapping in part with the first scenecovered by the first image capture device (13).

The arrangement described in this figure provides a nearly sphericalfield of view which is captured by the first image capture device (13)and an additional cylindrical field of view which is covered by thesecond image capture device (15). The two fields of view togetherprovide a nearly spherical field of view.

According to another embodiment of the present invention, optical zoomwithin the nearly spherical field of view can be achieved. Optical zoomwithin a sector that is acquired directly by an image capture device,meaning—without use of reflective lenses, can be obtained by control ofoptical zoom capabilities of the image capture device itself. Opticalzoom of a reflected sector is, however, more complex. Publication WO03/026272 describes several designs which enable optical zoom when usingreflective surfaces for coverage of a large field of view. An example ofsuch a design is illustrated in FIG. 5.

FIG. 5 demonstrates the imaging assembly that was shown in FIG. 2, withthe addition of optical zoom capability within the cylindrical field ofview. To achieve such capability, an additional reflective lens (16) isincorporated. The additional reflective lens (16) has different opticalqualities than the axi-symmetric reflective lens (17) and is capable ofreflecting a limited scene in different proportions than theaxi-symmetric reflective lens (17). The reflective lens (16) isincorporated at the center of the axi-symmetric surface (17) and is setto reflect a zoomed sector towards an imaging assembly, locatedcoaxially with the axi-symmetric lens (17).

According to yet another embodiment of the present invention there isprovided an imaging assembly that enables coverage of a full sphericalfield of view. The said assembly is based on the use of two imagingsystems, each provide a nearly spherical field of view. The imagingsystems being used are extensively described in publication no. WO02/059676. A first imaging assembly (23) is positioned to the back of anidentical or similar imaging assembly (18). Each of the two imagingassemblies is directed towards the opposite direction, and set tocapture a nearly spherical field of view. A preferable design is toposition the two imaging systems in conjunction with each other, inorder to ensure continuous cover of the entire spherical field of view,or with slight overlap in the fields of view that are covered. However,distance between the two imaging systems can be maintained, determinedaccording to the desired application and field of view requirements.

Reference is now made, in detail, to the first imaging assembly (23).The imaging assembly (23) includes an axi-symmetric reflective lens (19)which reflects a cylindrical field of view towards a second reflectivesurface (20). At the center of the reflective lens (19) exists a hole,under which there is positioned an image capture device (21), set tocapture the image that arrives through the said hole. Each light rayoriginating at a cylindrical field of view, which is covered by thereflective lens (19), will be reflected by the reflective lens (19)towards the second reflective surface (20). From there the ray will bereflected towards the hole that is locate at the center of thereflective lens (19) and will be captured by the image capture device(21). A hole also exists at the center of the second reflective surface(20), enabling an image of an additional scene to penetrate through thehole, travel directly towards the hole that is located at the center ofthe reflective lens (19) and be captured by the same image capturedevice (21) as the cylindrical scene. Overall, the image capture device(21) of the first imaging assembly (17) will capture two scenessimultaneously—a first, cylindrical, scene, and a second scene. The sizeof the second scene may be controlled by combination of additionaloptical lenses (22), thus by proper selection and placement of thoseoptical lenses (22) above and/or around and/or below the hole of thesecond surface (20), it is possible to achieve a second scene which iscontinuous to the first, cylindrical scene.

The same components and process may be described in reference to thesecond imaging assembly (18).

Rotation of the entire imaging assembly is also possible for purposes ofdirecting the image capture devices towards areas of interest, so thatan area of interest will be included in the “second scene” of one of theimaging systems, meaning the area of interest will not be captured asthe result of reflection, but as a result of direct capture by the imagecapture device.

Those skilled in the art will appreciate that although the figuresdescribe schematic hemispherical reflective surfaces, many designs forthose surfaces exist and the incorporation of a specific shape of thosesurfaces in the drawings should not limit the scope of the invention.

Although embodiments of the invention have been described by way ofillustration, it will be understood that the invention may be carriedout with many variations, modifications, and adaptations, withoutdeparting from its spirit or exceeding the scope of the claims.

1. A nearly spherical imaging assembly comprising an axi-symmetric lens,providing at least a reflection of a cylindrical field of view; a firstimage capture device, positioned coaxially with said axi-symmetric lens;and a second image capture device, set to capture an image, at leastpartially different from the image captured by said first image capturedevice; wherein, light rays from a first, cylindrical, scene arereflected by said axi-symmetric lens and captured by said first imagecapture device and light rays from a second scene, at least partiallydifferent from said first scene are captured by said second imagecapture device, said image assembly further comprising: wherein, a) thefirst image capture device is directed towards said reflective surfaceand set to capture the image that arrives from the direction of saidreflective surface after penetrating said transparent area in said firstaxi-symmetric lens; b) the second image capture device is positionedcoaxially with said second axi-symmetric lens, directed towards saidsecond axi-symmetric lens, and set to capture the image that isreflected by said second axi-symmetric lens; c) light rays from a first,cylindrical, scene are reflected by said first axi-symmetric lenstowards said reflective surface, reflected from said reflective surfacetowards said transparent area in the first axi-symmetric lens andtowards said first image capture device, and are captured by said firstimage capture device; d) light rays from a second scene penetrate saidtransparent area in said reflective surface, travel toward saidtransparent area in said first axi-symmetric lens, penetrate saidtransparent area, and are captured by said first image capture device;and e) light rays from a third scene, at least partially different fromsaid first scene are reflected by said second axi-symmetric lens towardssaid second image capture device and captured by said second imagecapture device.
 2. A nearly spherical imaging assembly according toclaim 1, further comprising optical lenses located at the exterior ofthe reflective surface, coaxially with the transparent area in thereflective surface; said optical lenses being designed to control theaperture of the second scene that is captured by the first image capturedevice.
 3. A nearly spherical imaging assembly according to claim 1,wherein the second axi-symmetric lens is positioned coaxially with thefirst axi-symmetric lens.
 4. A nearly spherical imaging assemblycomprising an axi-symmetric lens, providing at least a reflection of acylindrical field of view; a first image capture device, positionedcoaxially with said axi-symmetric lens; and a second image capturedevice, set to capture an image, at least partially different from theimage captured by said first image capture device; wherein, light raysfrom a first, cylindrical, scene are reflected by said axi-symmetriclens and captured by said first image capture device and light rays froma second scene, at least partially different from said first scene arecaptured by said second image capture device, said imaging assemblyhaving optical zoom capability and further comprising a reflectivesurface located around the central axi of symmetry of theaxi-symmetrical lens, providing an optically zoomed reflection of alimited sector towards the first image capture device; wherein, a) thefirst image capture device is directed towards said axi-symmetric lens,set to capture the image that is reflected by said axi-symmetric lens;b) the second image capture device is positioned opposite to saidaxi-symmetric lens; and c) light rays from a third scene comprising apartial sector of the first scene are optically zoomed and reflected bysaid reflective surface towards said first image capture device andcaptured by said first image capture device.
 5. A nearly sphericalimaging assembly according to claim 4, wherein the second image capturedevice is positioned coaxially with the axi-symmetric lens.
 6. A nearlyspherical imaging assembly comprising an axi-symmetric lens, providingat least a reflection of a cylindrical field of view; a first imagecapture device, positioned coaxially with said axi-symmetric lens; and asecond image capture device, set to capture an image, at least partiallydifferent from the image captured by said first image capture device;wherein, light rays from a first, cylindrical, scene are reflected bysaid axi-symmetric lens and captured by said first image capture deviceand light rays from a second scene, at least partially different fromsaid first scene are captured by said second image capture device, saidimaging device further comprising: wherein, a) the first image capturedevice is directed towards said first reflective surface and set tocapture the image that arrives from the direction of said firstreflective surface after penetrating said transparent area in said firstaxi-symmetric lens; b) the second image capture device is positionedcoaxially with said second axi-symmetric lens, directed towards saidsecond reflective surface, and set to capture the image that arrivesfrom the direction of said second reflective surface after penetratingsaid transparent area in said second axi-symmetric lens; c) light raysfrom a first, cylindrical, scene are reflected by said first axisymmetric lens towards said first reflective surface, then reflectedtowards said transparent area in said first axi-symmetric lens,penetrate said transparent area, and are captured by said first imagecapture device; d) simultaneously, light rays from a second scene, whichis at least partially different from said first scene, penetrate throughsaid transparent area in said first reflective surface, travel towardssaid transparent area in said first axi-symmetric lens, and are capturedby said first image capture device; e) simultaneously light rays from athird, cylindrical, scene are reflected by said second axi symmetriclens towards said second reflective surface, then reflected towards saidtransparent area in said second axi-symmetric lens, penetrate saidtransparent area, and are captured by said second image capture device;and f) simultaneously, light rays from a fourth scene, which is at leastpartially different from said third scene, penetrate through saidtransparent area in said second surface, travel towards said transparentarea in said second axi-symmetric reflective lens, and are captured bysaid second image capture device.